When a Lower Unit Price Costs More
A lower quote can cost more per usable unit under some loss and service assumptions. Compare total modeled cost ÷ usable units, counting each expense once; the worked example below is hypothetical, not supplier or industry data.
Define the Cost and Unit Boundary First
For this model, cost per usable unit = total modeled cost ÷ usable units. Define the period and what happens to damaged and defective goods before entering costs. All dollar amounts below are assumed USD inputs, not current quotations.
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| Input | Assumed scope | Why it matters |
|---|---|---|
| Purchased quantity Q | 5,000 adapters per candidate | Purchase cost is Q × unit price |
| Transit losses L | A: 140; B: 8, not replenished | Usable denominator is Q − L |
| Customer replacements | A: 175; B: 20, all restored | Incremental replacement cost counted once |
| Cost period | Shipment plus the assumed return window | Include the same period for both |
The replacement costs below assume full incremental replacement/service costs with no recoveries. Customer replacements restore the affected delivered units, so they do not reduce the final usable count again. Transit losses are not replaced in this scenario. Both candidates therefore fall short of a 5,000-unit usable-delivery target.
Common mistake: Adding the purchase value of crushed goods to purchase spend again. That value is already included in Q × price; here its effect appears through fewer usable units. Takeaway: Choose one treatment for each loss and avoid counting it twice.
Cost Categories to Record
Record purchase, inspection/rework, freight, incremental replacement/service and administration costs separately. Add delay costs only with a stated basis; the example includes an assumed economic allowance, so its total is broader than cash landed cost. A failed inspection or documentation gap can add costs, but a low price alone does not establish that either will occur.
Takeaway: Use project records or explicit assumptions instead of “typical” defect or spare rates.
Total Cost Comparison: Assumed Inputs
This entire comparison is hypothetical. A and B are labels for assumed inputs, not real suppliers, certification grades or evidence that cheaper products are generally worse.
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| Cost or quantity | Candidate A | Candidate B | Treatment |
|---|---|---|---|
| Unit purchase price | $7.20 | $8.10 | Assumed price per ordered unit |
| Initial purchase, 5,000 units | $36,000 | $40,500 | Count once |
| Inspection | $650 | $325 | Assumed incremental expense |
| Delay allowance | $900 | $0 | Assumed economic cost |
| Freight/handling | $2,400 | $2,550 | Original shipment |
| Transit loss | 140 units | 8 units | Reduce denominator; no extra purchase-loss charge |
| Customer replacements | 175 × $18 = $3,150 | 20 × $19 = $380 | Assumed incremental replacement/service expense |
| Administration/support | $1,200 | $200 | Assumed internal cost |
| Total modeled cost | $44,300 | $43,955 | Sum cost rows; exclude loss quantity |
| Usable units | 4,860 | 4,992 | 5,000 minus unreplaced transit losses |
| Cost per usable unit | $9.12 | $8.81 | Round only after division |
| Cost per ordered unit | $8.86 | $8.79 | Separate denominator: 5,000 |
A = (36,000 + 650 + 900 + 2,400 + 3,150 + 1,200) ÷ (5,000 − 140) = $9.1152… per usable unit. B = (40,500 + 325 + 0 + 2,550 + 380 + 200) ÷ (5,000 − 8) = $8.8051… . Under these assumptions, B has $345 less total modeled cost and more usable units. Takeaway: This result applies to these inputs; changing losses or service costs can change the comparison.
Copy an Adjustable Calculation Table
Copy the table into a spreadsheet with its header in row 1 and its first input in row 2. Enter numeric USD amounts without currency symbols in columns B and C; replace the assumptions and keep the formulas. The usable-unit denominator must remain positive.
Scroll horizontally to see all columns if needed.
| Spreadsheet column A | Column B: A | Column C: B |
|---|---|---|
| Purchased quantity | 5000 | 5000 |
| Unit price | 7.20 | 8.10 |
| Inspection | 650 | 325 |
| Delay allowance | 900 | 0 |
| Freight | 2400 | 2550 |
| Replacement/service expense | 3150 | 380 |
| Administration | 1200 | 200 |
| Unreplaced transit losses | 140 | 8 |
| Total modeled cost | =B2*B3+SUM(B4:B8) | =C2*C3+SUM(C4:C8) |
| Usable units | =B2-B9 | =C2-C9 |
| Cost per usable unit | =B10/B11 | =C10/C11 |
| Cost per ordered unit | =B10/B2 | =C10/C2 |
If transit losses are replenished, record the incremental replenishment expense and the restored unit count consistently. If customer replacements are incomplete, revise the final usable count too. Deduct documented credits/recoveries from costs once; avoid overlapping replacement and support charges.
Takeaway: A spreadsheet result is only as comparable as its period, cost boundary and unit definition.
How to Use the Model in a Sourcing Project
Use the specification comparison guide to establish equivalent products, the quality-control workflow for acceptance evidence, and the first-order checklist for remedies and payment milestones. Negotiate any spare allowance explicitly rather than assuming a fixed percentage. Our supplier evaluation guide helps record capability evidence without inferring quality from price.
How this guide was prepared
An editorial cost model with assumed inputs and AI assistance, not observed orders or market prices. Totals are independently reproducible from the displayed formulas. No price-quality relationship or typical defect/spare rate is inferred.
Found an error? See our corrections policy and research methodology.
